In recent years, brake control devices of vehicles have been studied in which a braking force is assisted by electric power used as a drive force in response to brake-pedal operation. Such brake control devices are operated by supplying electric power from vehicle power supply sources. Thus, if there is a malfunction of a vehicle power supply source, it results in loss of operation. In order to cope with loss of operation, a brake control device that is electrically operated has a mechanical configuration in which a brake pedal depressing force is transmitted to the braking system of each wheel to cause generation of a braking force.
However, it is desirable for such brake control device to use electric power as a drive force to a maximum extent. JP Patent Application Publication No. 2004-17732 A (Patent Document 1) discloses a related technique. Patent Document 1 discloses a method for supplying electric power from an auxiliary power supply source when there is a malfunction of a main power supply source of a brake control device.